Flash-back indicator for mercury rectifier tubes



J. w. CONKLIN ET AL 2,089,994 FLASH-BACK INDICATOR FOR MERCURY RECTIFIER TUBES Filed Jan. 10, 1934 2 Sheets-Sheet 1 Aug. 17, 1937.

N .HANSELL QM INVENTORS JAMES W.CONKLI CLAR NCE W ATTORNEY Aug. 17, 1937.

' J. W. CONKLIN ET AL I FLASH-BACK INDICATOR FOR MERCURY RECTIFIER TUBES Filed Jan. 10, 1934 2 Sheets-Sheet 2 INVENTORS JAMES w. CONKLIN BY CLARENCE W.HAN5ELL Patented Aug. 17,1937 V UNITED STATES PATENT OFFICE] v msli-Bacl tm lgz gf ggg MERGIlBY I James w. oei'iiuiri and ciareiiee w. Hansen,

1 Rocky Point, N. million to Radio Corporation of America, a corporation of Delaware Application January 10, 1934, Serial No. 706,018

1; Claims. ((1. 117-311) I This invention relates to a flash-back indi- The requirements therefore for a satisfactory cator which is particularly adapted for registerflash-back indicator are that they should indiing flash-back failures in high voltage mercury cate only at the moment of excessive currents arc rectifiers. in,a reverse direction and shall be capable of car- An object of this invention ,is to provide a rying the normal rectification current also any 5 simple and improved electrical indicatingd'evice. momentarily external overload currents without Another object of this invention is to. provide a visual indication or damage to the rectifier tube.

' flash-back indicating device which empioys but-a The visual indicator member of this invention few inexpensive component parts, each of the is a red painted rod-like member no'rmally held separate component parts specifically performout of sight within a tube by a permanent maging several functions wherever possible. net.

Another object of this invention is to provide A more complete understanding of this iman improved flash-back indicator which does not proved indicatorwill be had by referring to the employ the use of pivots which are common to accompa yi g drawings, in which,

most all polarized relays or indicators, all of Fig. 1 shows afundamental circuit of the mag- 15 the prior art indicators having one or more pivots netl ac ion of th i di .Whe h current is in their general construction. flowing in the normal direction;

A feature of this invention is the simplicity 2 Shows a d a m o e magnetic action with which the indicator may be connected and 0f the indicator when h Current is flowing in ac assembled to existing rectifying apparatus. the reverse direction;

Another feature of this invention is the adop- Fig. 3 is a vertical longitudinal section of the tion of auxiliary contacts to be opened by the indicator; L falling of a visual indicator for the purpose of Fi 41s an elevation of Fi operating auxiliary alarm or control circuits Fig. 5 is a cross section of Figs. 3 and 4, the- 28 which may be remotely located. section being taken on lines AA of Fig. 3; Y

Rectifier tubes as used for supplying direct Fig. 6 is a section of the lower part of 3 i current in high voltage circuits employing the showing an arrangement of auxilia y n a s;

hot cathode mercury vapor type tubes such as Fig. 7 is a circuit diagram of the auxiliary conthe UV-869A are subject to occasional failures tacts as shown in Fig. 6.

30 commonly termed flash-backs or arc-backs, in Referring now to Figs. 1 and 2 which indicate 30 which the tubebreaks down and becomes conthe fundamental magnetic circuit and upon which ducting in a direction reverse from the desired P p e e ndi a Wo s, I indicates 8 D and frequently results in failures of the radio 2 being enclosed within a solenoidcomprisinga transmitter. When such tubes are subjected to coil 3 of a few conductor turns which is serially flash-backs they may or may not display any connected in the operating circuit. Inthe normal 40 visual indications which will enable an operator operation of the rectifier circuit the coil 3 will to readily be aware of such an occurrence. magnetize the soft iron armature 2 with the same The purpose of this invention is to furnish polarity as the permanent magnet I, causing the means by an improved type of flash-back indiarmature 2 to be held tightly to the magnet I. cator to identify immediately the tube or tubes in When currents flow in the reverse direction, such which flash-back has occurred. Thecurrent as occurs in a flash-back, there is set up a reverse 45 flowing through two rectifier tubes during. the polarity in the iron armature 2, causing it to opmoment of flash-back, as mentioned above, are pose the permanent magnet and force, the armaof excessive magnitude, and of the same order ture away from the magnet I. The lower end of as those occurring with 'an external flash-over the magnet .l is surrounded by a short circuited in the rectifier circuit, and are similar in nature turn in the form of a copper sleeve 4 which supto those occurring in a power amplifier flashplies a time lag to the current fiow and opposes over. They are difierentiated however from the any rapid change of the flux flowing. through the normal overload currents in that the direction of permanent magnet l. The action of this short the direct current flow in the faulty tube is re-. circuited turn being two-fold in that it serves to versed from the normal rectification currents. momentarily maintain the polarity of the permanent ma'gnet against the action of the solenoid 3 and prevents any demagnetization of the permanent magnet caused by high reverse currents in the solenoid. Fig. 1 shows the approximate conditions of the magnetic fiux and the current in the normal di-- rection, and it will be noted that the flux is substantialiy continuous through the armature and magnet,

In Fig. 2 there is shown the conditions existing when the momentarily reverse current has just been applied,and it will be noted that there ,are two opposing fields set up, one being produced by the solenoid 3 and the armature 2, and the other field being that of the permanent magnet. It is also to be noted that when a normal field exists at the junction of the two fields, as indicated by the dotted fiux line 5 shown only in Fig. 2, during the duration of the reverse current this neutral field progresses gradually upward as the solenoid field gradually overcomes the efiect of the short circuited turn 4. When a neutral field approaches the division point between the armature and the permanent magnet,'the magnetic forces tending to hold the two elements together will be momentarily weakened and the armature released. When the armature is released it drops by the action of its own weight assisted by the action of the solenoid attempting to centralize the armature within itself. Once the armature is released from the magnet l and dropped beyond the influence of the forces of the permanent magnet field l the magnetic force of the permanent magnet is no longer sufficient to raise it, and the indicator or depending rod portion 8 remains in this lower or dropped position until the circuits have been corrected and the armature 2 manually reset. 7

Referring now to Figs. 3, 4 and 5, there is shown the general mechanical assemblage of the various component parts. The unit is normally mounted ina convenient position adjacent to the rectifier tube and connected directly in series with the plate or cathode lead of the rectifier tube by means of terminal lugs l and 8. Interposed between the terminal lugs there is retained a tubular insulating housing 9 having end terminal and closing ,members Hi and H. Surrounding the insulating member 9 there is wound the cop- 0 per solenoid 3 which is serially connected between end terminals l8 and Ii. Located in the upper portion of the unit there is retained a threaded copper tube l3 which is secured to the end terminal member l0 by means of a screw I4.

5 Within the member i3 there is located the permanent magnet rod l, the location: of the ma net within the member |3 being determined when the flash-back indicator is adjusted in the circuit by means of clamping or set screw i5. Directly below the magnet I there is located the soft iron armature 2 which is threaded to receive the depending indicating rod portion 6,

- preferably composed of insulating material such as bakelite. The lower end of the indicating rod insulating member l2. The armature is movably located within a lower copper tube It which is similar to member l3 and is retained within the insulating housing 9 by means of a suitable screw H, the whole assemblage being retained between the terminal lugs l and 8 by means of clamping nuts l8 and IS. i

In another method of mounting the indicating device the terminal lugs 'I and 8 may be dispensed portion 6 is painted red, as indicated by the dash and dot line. The solenoid 3 is covered by an with and the entire unit retained by a pair of standard cartridge fuse clips which are mounted on a suitable panel. By this modification of mounting several different indicating devices having varied electrical characteristics may be quickly interchanged.

is located directly below the clamping nut iii an insulating bushing 20 which retains a-contact member 2i. There is also located on bushing 28 a similar contacting element 22 which is spaced apart from contact spring 2! by means of an insulating washer 23 and clamped by means of a nut 2d,,the nut 2% being insulated from the contacts by means of an additional washer 25. The extreme or free ends of spring contact members 2| and 22 are provided with suitable contacting material such as silver or tungsten points 25 and 2?.

In the circuit shown in Fig. '7 the contacts 2i and 22 are shown connected toa suitable bat- ,tery 28 which is arranged to operate a bell 29 or any other indicating device upon the closing of the circuit by means of contacts 2i and 22.

In the'adjustment of this improved flash-back indicator the magnet l is normally held per-. manently in place by the set screw H5 in the end terminal member iii. The set screw i6 is loosened only when adjusting or removing the magnet. Normal adjustment of the magnetis with. its inner pole just flush with the inner end face of the upper tube l3 and making contact with the iron armature 2. This adjustment may be obtained by holding .the unit inverted and pushing in the magnet until it just starts to raise the plunger or by forcing the magnet in until it moves the plunger and then pushing it back to to its normal position. This Qnay be accomplished by applying pressure on the plunger with a special tool. The north end of the magnet which is preferably associated with the upper terminal, should point in the direction of the positive terminal of the unit for the normal how of current. R

The sensitivity of the indicator 'may be increased by withdrawing the magnet into the tube I3. However, such adjustments are uncertain as to their accuracy. The magnet i should be just strong enough'to support three or four times its own weight of iron from one pole. If the permanent magnet should become weak its field strength can be very easily replaced by remagnetizing, or it may be remagnetized by forcing a momentary current of several. hundred amperes through the coil 3 in a direction of the normal rectification current, any ordinary 8-volt direct current potential being satisfactory for this purpose. This large amount of current should be maintained only for an instant as a longer period of time will overheat the solenoid and thus damage its insulating q lities. Therefore, it is better whenever practical to remove the magnet and remagnetize it by any suitable external remagnetization method.

A number of indicators tested in actual circuit operation showed that when occasionally they were demagnetized by excessive arc-backs, normal circuit operation of the indicator restored the magnetism without further attentiom While I have described only one specific use for this invention, it is distinctly understood however, that this indicator is capable of uses in other circuits, and therefore the invention should not be limited'except as imposed by the appended claims.

What we claim is:

1. An electrical device to be used as an indicator for the direction of a desired normal current flow comprising a permanent magnet partly loan insulating tube, a single shortcircuited turn through said solenoid. 2. An electrical device to be used as an indicator for a normal current flow comprising a permanent magnet located within an insulating tube, a single short-circuited turn of copper acting through said solenoid.

4. An electrical device to be used as an indicator of the normal flow of direct current comsaid solenoid is rever I 5. A device to be used as an indicator for the normal flow of desired direct current comprising i field of said permanent magnet a permanent magnet the lower portion of which is surrounded by a single short-circuited turn of metal acting as a coil, an armature normally held the magnetic atmagnet, a single surrounding said armature and located below said short-circuited turn, indicating means attached to said armature comprising a rod-like member the lower portion of which visually indicates when sired direct current layer coll. v

ii. An electromagnetic device of the pivotless the normal flow of the deis reversed in said single ype for indicating a desired normal direction of current flow comprising an insulating tube, a

mal position relative to said permanent magnet, a winding surrounding said armature which produces a field aiding the magnetic field of said magnet when current flows in a nordirection through said winding, and also a magnetic field opposing the field of said permanent magnet when the current flows in direction through said winding surrounding said armature.

JAMES W. CONKLJN. CLARENCE W. ANSELL,

within said tube, and anv to assume 8 nor- 

